An UnderFell Love Story
by Kamije Celeek
Summary: AU: Asriel was a selfish prince who never really cared about anyone other than himself. That was probably the reason he ran away to the Ruins. However, when a human girl falls down, he begins to fall in love with her, leading down an unexpected path.


**If you've been following me for a while on this site, then you know that I have a tendency to get into new things at the drop of a hat. This has to do mainly with Underfell right now, but I'll get back to that later.**

 **This is partially an observation I've made in all the time I've spent in the fanfiction archive on this site with Undertale shipping for Frisk. If Frisk is female and has a more cute and classically romantic relationship, or that's what the shipper** _ **wants**_ **, she's going to be more likely than not shipped with Asriel. If Frisk is female and has a more speedy and sexual romantic relationship, that falls in the Sans and Frisk category. I'm not saying this is always the case, and feel free to correct me, but it's just what** _ **I**_ **personally noticed.**

 **What does this have to do with Underfell?**

 **It actually ties into the fact that, as far as Underfell goes, Friskriel doesn't exist. Underfell seems to just be an excuse for some people to write Sans as a sexual predator, or as a rapist, or write dom/sub lemons. And it's** _ **only**_ **Sans. I know this fandom loves the guy, but holy** _ **shit**_ **do they take it too far!**

 **My thought with this story was that I'd be one of the few to write a Frisk and Asriel Underfell fanfiction. Seriously, take a look around and see how many you find. None on this site, as far as I know.**

 **To be completely honest, I've never been on board the S. S. Sans X Frisk. In my mind, they have the same relationship as a child and older relative. Asriel is just, in my mind, a better choice.**

 **This is an AU of an AU, as weird as that sounds, where Asriel never died and a lot of monsters became dicks for no reason other than the fact they lost their minds underground. He left home for no reason other than the fact that he wanted to, and decided to live in the Ruins. I know it messes up the timeline, but this is** _ **my**_ **story, goddammit, not yours!**

 **One final note/warning is that this is the first lemon that I've ever written. It won't be very explicit and won't include the actual act, but it will contain what leads up to… *ahem* the nasty, such as groping, Frenching, getting naked, and a teensy bit of grinding. That being said, this story will be rated M for that reason. Sorry to my younger readers, but this isn't for you.**

* * *

Living in the Ruins gave him a sense of superiority.

He was, by far, the most advanced monster living there, and it made him feel like he was untouchable. He was free. Free from humans, from his parents, from his goody-two-shoes sister…

Still, it was a teensy bit lonely at night, when there wasn't anybody to talk to… but he didn't care. He didn't need anybody or anything!

Or so he thought, until the day a human fell into the Ruins.

It had started out normal—wake up, eat breakfast, terrorize the other monsters—until he found his way to the hole his sister had fallen through when they were children. Below that hole was a patch of golden flowers and in this patch of flowers was a human. They were lying there, seemingly dead.

He considered taking their SOUL for a moment before deciding against it and turning them over.

It was a girl. A human teenager.

She had short brown hair and tan skin. She wore a blue sweater with pink stripes that went well with her jeans and boots. And she wasn't dead; just unconscious. She looked so peaceful. Too peaceful.

"Hey!" Asriel barked, shaking her like a ragdoll. "Wake up!" Her eyes fluttered open. To his shock, they were two different colors; one green and one blue. She blinked and let out a gasp as she stared at him.

"Y-You're—"

"A monster. That's right, baby. And you're not getting out of here."

"Where can I go?"

"Eh. I guess you could stay here, if you don't mind cleaning or cooking." To his surprise, her face lit up.

 _ **God**_ **,** _she's cute. Wait, what the fuck am I saying?!_

"I'm Frisk," she introduced herself, struggling to stand up. He instinctively caught her before she fell back into the buttercups. "Sorry!"

"You should be. I'm Asriel."

"It's nice to meet you!"

"I'm not nice."

"You woke me up, didn't you? I have a feeling most monsters wouldn't have done that."

"Yeah, but that doesn't mean I'm nice. I just didn't want you lying around doing nothing."

"Well, still. Thank you." She took his large paw in her own delicate hand, and he felt warmth rushing through his body, a warmth unfamiliar to him.

 _What did she do…?_

* * *

Once Frisk was settled in, she kept the little house in the Ruins in the best possible condition, and made sure there was plenty of food, which involved leaving the Ruins. She stayed, which baffled Asriel to no end. He'd assumed that she'd stay a couple days and leave, not move in!

To add to his confusion, he felt nervous around her, and whenever she'd talk to him, that warmth would return and make its way through his body. He didn't like it, even though it felt nice. He still refused to answer any of Frisk's questions or tell her anything, giving her a completely frozen shoulder.

And yet… she kept trying, until it happened.

"Why are you being so nice to me?" he asked.

"My mom," she replied. "She used to tell me, when I was really little, that I should show kindness to everyone, and that would make the world a better place to live in."

"Seriously?"

"I've lived by those words, and my life sucks, but at least I can make the people around me happy, right?"

"What happened to your mom?"

"When I was eight, she got really, really sick. Dad and I took care of her the best we could, and she pulled through… for a little while. She lost the fight when I was ten. Dad and I grew apart and started arguing more. It hit a peak about a week before I fell down here, and he disappeared. That's why I was up on the mountain."

Suddenly, Asriel felt like a royal asshole. Here he had been, complaining about his family, and here she was, talking about how much she cared about a relative she argued with on a regular basis. She'd lost everything important to her, and she still cared about people she barely knew.

Did that include him?

"I'm sorry… about your parents."

"I miss them, but at least I'm not alone."

She smiled at him.

* * *

Time passed. Asriel gradually began to warm up to Frisk, though he kept a frozen heart. They'd occasionally leave the Ruins together so Asriel could show her some out-of-the-way spot in the Underground.

"This is so pretty!" Frisk gushed, staring at the ceiling of the Wishing Room. "I mean, they look just like stars!" Asriel let out a sad sigh. "What's wrong?"

"You're gonna think it's stupid and corny."

"No, I won't! What is it?"

"I wish… I wish I could see the _real_ stars someday, not this twinkly-stone bullshit on the roof of the cave."

"That's not stupid _or_ corny! That's sweet!"

"I'm not supposed to be sweet!"

"Well, too bad, because you _are_ sweet."

They were face-to-face, just inches away from each other. He closed his eyes and leaned forward nervously, his lips barely brushing hers before making full contact. She returned the kiss with as much enthusiasm. When they broke apart, both were blushing profusely.

"Wow…" Asriel muttered.

"I've never kissed anyone before…" Frisk confessed.

"Neither have I."

* * *

Weeks passed. Frisk and Asriel became less like slightly awkward acquaintances and more like a married couple. He loosened up quite a bit and told her about his parents and sister. She listened, which he appreciated. It made him feel happy for the first time in a long time.

As their relationship grew, the warm feeling Asriel had felt began to grow into a burning heat. It was hard to ignore at times, especially when she was touching him (by holding his hand, kissing, sitting next to him, or hugging, ya pervs), but he managed to control it. He was still confused by why it happened in the first place.

Frisk was different from anyone else he'd ever met, and not just because she made him feel the way that he did. It had something to do with how kind she was, the fact she laughed at his jokes even when they weren't that funny, and the way she never thought about herself.

Then came that night.

"Did you find anything?" Asriel asked as Frisk came back from Snowdin.

"Yep, but that taller skeleton sentry was giving me a hard time again," she replied, setting down her bag and taking off the hooded cloak that concealed the fact she was human. "I think Sans follows me when I leave."

"That's just because he's keeping an eye socket on you."

"I wish I didn't have to hide."

"I know, but we don't really have a choice. It's either hide or get caught and turned over to the Royal Guard, and I don't want to lose you to Undyne."

"Thanks, Asriel. You always know what to say." She kissed him on the cheek before going into the kitchen to put away groceries and get started on dinner.

Once dinner was over, they sat on the couch, watching a movie on an old TV and DVD player they'd found at the dump. There was no way they were watching any of the Underground's programming; it was all Mettaton, anyway.

Contented, Frisk snuggled closer to Asriel. He put his arm around her and his hand brushed… something… concealed by her oversize sweater. He'd never seen her without it, but he still felt slightly intrigued. Curious, he moved his hand back over it and this time squeezed whatever it was. Frisk let out a little gasp, and he pulled back. She grabbed his hand.

"N-no… K-keep going…" she pleaded, her voice trembling.

Wanting to find out what he was touching, he pulled off her sweater and discovered the figure she'd been hiding from him (here's your pervy part, guys): large breasts and hips, with a small waist—the kind he'd heard his male friends begin to talk about shortly before he left home. The burning heat began to expand deep inside him as he looked at her.

Suddenly, instinct told him what to do. He turned off the movie and pinned Frisk to the couch. She was startled but looked curious as to what would happen next. He removed her shirt and began kissing her fiercely, inserting his tongue into her mouth. Hers rose up to meet his and she moaned through the wrestling.

It felt _good_. Frisk lightly bucked her hips against him, causing him to want more. He took off her jeans, leaving her in just her bra and panties. She removed his jacket as he continued to kiss her, and then off came his shirt and pants, leaving him in just his underwear.

Wanting to pleasure her more, Asriel stopped kissing her long enough to rid her of her bra, her breasts bouncing as they were freed. Without thinking, he tentatively touched the tip of his tongue on one of her hardened nipples before putting his lips around it and sucking. She let out another moan of pleasure and bucked against him again, the heat in his belly now making its way towards another part of his body.

Taking off her panties and throwing them aside, Asriel felt his underwear tightening in the front as he gazed at the entirely-naked Frisk, who had half-lidded eyes and a look that plainly begged, "Fuck me as hard as you can!"

So he did.

"Well," he panted once they'd finished. "That was…"

"Amazing," Frisk agreed dreamily.

"If you ever want to… you know… again, we can."

"I'd like that."

"I thought you might. I'd like it, too. Let's… go to bed."

After that first time, they did it on a regular basis, like eating and sleeping. It became a part of their day-to-day lives, and they couldn't have been happier.

Unfortunately, of course, happiness doesn't last forever. Theirs came to an end much sooner than they would've thought or liked.

* * *

Asriel began to get worried. Frisk wasn't home yet, and she never took this long to get what she needed unless something was wrong. He needed to check on her.

He put on a hoodie and covered his head, heading out into the Snowdin Forest to try and find her. The former prince thanked God that the dogs on the Royal Guard were stupid, and weren't able to smell him. However, he came across three Snowdin residents who were having a conversation. When he heard the subject of their conversation, he swore his heart stopped.

"Did you hear they caught a seventh human?" a woman whispered to another.

"Yeah!" the second woman replied. "I heard Papyrus has been suspicious of her for months but wanted to be sure before he handed her over to Undyne!"

"I heard she'd been coming to town all that time to buy supplies!" a man added on. "A human, in town, and we didn't know! I would've taken her SOUL on the spot!"

They said more than that, but it became muffled as Asriel took in what they'd said at first.

Frisk had been caught by one of the Royal Guard and taken away. Heart pounding again, he knew he needed help, and asking his family was out of the question. There was only one option left.

Sans.

* * *

Sans groaned as a knock sounded at the door. It turned to frantic banging as he took his time to get there.

"All right!" he snapped, opening the door. "Whaddaya—"

To the smaller skeleton's shock, the former monster prince was standing outside in a cloak. He had an extremely worried expression.

"Asriel? What are you doin' here?"

"Let me in, Sans, and I'll explain, but we have to hurry."

Sans shut the door and turned to Asriel.

"Go on, kid. What's wrong?"

"Frisk… Frisk got caught."

"The fuck?! Seriously?!"

"Papyrus turned her in today. I heard some monsters in town talking about it."

"Oh, God… poor kid."

"I want to save her, but I'm not much use on my own. I need you to help me. I can't—I can't lose her."

"I get it. You've got my help. But I'm not doin' this for your selfish ass. I'm doin' this for Frisk. She's a good kid and doesn't deserve it."

"Thank you so much!"

"Heh. She's really rubbin' off on ya, in more ways than one."

* * *

Frisk sat in her cuffs, kicking her feet nervously as she waited for Doctor Alphys to get there and scan her SOUL to make sure it was the right kind. If it wasn't, she'd be thrown into prison to rot for the rest of her life. If it was, she'd be killed and her SOUL harvested to destroy the barrier.

The nausea that had been plaguing her for two weeks now decided to pop up. She vomited into a nearby trashcan and sank back into her seat.

She wanted Asriel there with her.

* * *

"Now, from what Papyrus the Jackass has told me," Sans told Asriel as they spied on Alphys's Lab, "any human caught in the Underground gets their SOUL scanned before they're killed to make sure it's the right kind of SOUL. Judging by the time when Frisk was captured, she should be in there now."

"So, what's the plan?"

"I'll get us in there. You grab Frisk, take her back to the Ruins, and fuck her until she barely remembers her own name."

"DUDE!"

"C'mon, you really thought I didn't know about you and Frisk having enough sex to make _rabbits_ look bad at fucking each other? It was obvious."

"Damn! I hate you sometimes."

"Yeah, I hate me, too. Now, let's get in there and grab your girl."

* * *

Alphys lowered the SOUL scanner over Frisk. She'd never really used it on a human before, since most humans had fallen when her predecessor was Royal Scientist, but she knew exactly what she was looking for.

And what she found was both expected and unexpected.

A second SOUL inside of the human, this one half monster as well, and too faint to be a full being.

The human was pregnant.

* * *

The Lab was fairly easy to get into. Asriel and Sans made their way through the part of the Lab they showed the common monsters and down to the basement, where the True Lab lay. Asriel lit the way using his fire powers while Sans checked every room.

Frisk was in the operating room, they discovered through the one-way mirror that allowed them to see in but nobody to see out. Alphys was nowhere to be seen, so Sans opened the door to let Asriel in.

"Asriel!" Frisk sobbed happily as he hugged her. He stroked her hair gently.

"Frisk, I'm so happy you're okay," he croaked.

"Sorry to interrupt your little reunion, but we've gotta go, lovebirds," Sans announced. "Save it for later, when you're fucking each other senseless."

"C'mon!" Asriel grabbed Frisk's hand and pulled her behind him.

The trio had just left the room when they ran straight into the doctor. She calmly straightened her glasses and gave them a smile.

"Frisk, stay behind me," Asriel told Frisk. She nodded and backed away. "You're _not_ taking her!" he growled to Alphys.

"It's nice to see you again, Prince Asriel," she replied smoothly. "Protecting humans now, I see? Or is she your lover?" He twitched at the accusation, and she smirked. "I see you're as bad at keeping secrets as ever."

"What do you want, Alphys?" Sans snapped.

"Oh, nothing, actually. I was just wondering if the prince knew about her condition."

"What condition?" Asriel and Frisk asked in unison.

"Frisk, I was on my way to deliver some news. First of all, you have the right kind of SOUL we need." Frisk buried her face in Asriel's arm. "And… congratulations. You're not going to be killed just yet. We still have _some_ morals down here." She lifted her face.

"What are you saying?" Asriel demanded to know.

"I'm saying she's pregnant, and I'm assuming you're the baby's father since she doesn't have any signs of being raped in the past month-and-a-half and Sans here doesn't have the equipment."

"Fuck you" was Sans's response.

"What?" Asriel asked, dumbfounded. Frisk looked just as confused.

"Look, I'm going to be nice here. I'll tell Asgore Frisk had the wrong kind of SOUL and that her SOUL disappeared so you two can go back to the Ruins, raise the baby, and live happily ever after, deal?"

"O-of course!" Asriel agreed. Frisk hugged his arm the best she could with her handcuffs on.

Sans got them back to the Ruins in one piece. He unlocked Frisk's handcuffs but let her keep them, saying it might make things more… interesting (and by that he meant kinky).

* * *

Asriel and Frisk began to deal with the reality of the fact that they were going to be parents. The baby would be a hybrid, the first one born in years. It also meant that they couldn't do as much as they wanted when it came to sex, since it could hurt the baby. Sans took care of bringing them basics (reluctantly, but he didn't want Frisk to die) so there was no reason to leave the Ruins.

This brings us to where they actually used the handcuffs, their first time having sex since finding out about Frisk's pregnancy.

* * *

It had been one of those days where nothing really seemed to happen. They went about their normal schedules, doing what they normally did, until that night.

That night, Frisk had been just about to change into her pajamas when Asriel came into the room they now shared, the door slamming shut behind him as he kissed Frisk hungrily. She kissed him back with as much gusto while he slid his jacket off. He then pushed her onto their bed while she giggled like crazy.

They undressed each other and he was about to go straight for her breasts when she held up a hand.

"I have an idea," she told him, sliding off the bed and grabbing the handcuffs off the dresser. She held them out to him. "Cuff me and fuck me."

"I fucking love you. Come here so I can arrest you for being too sexy."

He cuffed her hands together after securing her to the headboard. She had an innocent look on her face, one that a criminal mastermind might use to get out of jail, but one that made him want to fuck her more than ever. Still, he had to prep her for it. Her bra was still on along with her panties, he realized, so he decided to try something new.

"Before I haul you off, how about I show you the penalty for being too sexy?"

Her reaction was perfect; he could see her shivering in anticipation. She glanced at her bra and back at him, obviously expecting him to remove it, but he didn't oblige.

Instead, he flipped her onto her stomach and slid her panties down her legs so her bare ass was right there. He leaned towards her ear.

"Your punishment starts now," he whispered sexily, lightly tapping her butt. "This ass is mine, then I fuck you, got it?"

She whimpered and nodded, giving him the go-ahead. He raised his hand and slapped her ass, not too hard, but not a light tap either. Frisk let out a noise that sounded like a moan and a squeal of pain at the same time.

"M-more!" she begged.

"What do you want more of?"

"Y-you s-slapping my ass."

"That's going to get awfully boring."

"Harder."

"What?"

"Slap my ass harder!"

"Whatever you say."

He slapped again, harder this time, and his hand left a red mark on her bare skin. She let out another pain-filled moan as the sound filled the room.

"Anything else?"

Oh, yeah. He was getting a kick out of this. She was going to be so ready for him.

"Tongue."

"Upper or lower lips?"

"Upper or l—" She started to ask him to clarify, then her eyes widened. "Lower, please! Tongue lower!"

He flipped her onto her back again and spread her legs wide enough for him to get through. His tongue teasingly touched her lower lips before she broke down.

"JUST DO IT! PLEASE! I CAN'T TAKE IT!"

He fully inserted his tongue and wiggled it around. She moaned louder than she'd ever moaned before when they were having sex, one that begged him to stop messing around. He obeyed… to an extent.

Instead of taking off his own underwear and mindlessly fucking her, he unclipped her bra and tossed it away like an offensive piece of garbage (which, in that situation, it was to him). She gave him a confused look before he hovered over one of her breasts and took the nipple in his mouth. He bit down on it while the fingers on one hand pinched the other nipple tightly. The fingers on the other hand were a lot further south and lost inside of her. She was writhing with pleasure and could barely form a coherent thought.

"I think you've been punished enough," he informed her as he released her breasts and recalled his other hand. She stared at him, quivering with need, before he went in for the kill (and orgasm).

Her pleasure-filled screams echoed throughout the Ruins.

* * *

As months passed and her pregnancy dragged on, Asriel became less predatory and more sweet and attentive towards the mother-to-be. He was the one who helped with all her weird cravings and mood swings and morning sickness… and her increased sex drive in the second trimester.

Sans entered the house in the Ruins with a bag of groceries. Frisk was asleep on the couch, her hair messy from more than sleep, he assumed. At least she was wearing clothes.

When he'd met Frisk, he'd known she wasn't a monster by the way she acted. Every monster in the Underground (except the Queen) acted like a complete and total douche because they were sick of being stuck there. She'd treated him with kindness, something he hadn't known since his own mother passed away and Papyrus became obsessed with human-hunting. He'd followed her back to the Ruins, where he introduced himself to her properly. She was gracious and sweet, the kind of kid he wouldn't mind having as offspring.

That's probably why he thought of her as a daughter.

He knew, somewhere, far away, there was somebody who saw him in the position Asriel had been in before Frisk got pregnant but after she and Asriel had started having regular sex, but he didn't care. Dads were supposed to take care of their kids, not do that kind of stuff.

He'd leave it to Asriel.

* * *

The first thing she felt when she got up that morning was a slight pain near her… area. Frisk noted Asriel wasn't in bed at all, meaning it wasn't him. She got up and staggered to her feet. Out of habit, she looked down at her swollen belly. It was huge, and according to Sans, the baby was due any day now.

The pain sharpened a tiny bit, but she ignored it and went out to get something to eat.

Alphys came over a little bit later with Sans, just to check on Frisk, when the human girl's water broke. The baby was coming.

Asriel was freaking out, but managed to hold onto her hand while she began the long and difficult process of birthing a child. She squeezed his hand so hard, he felt like it was about to break.

Hours later, Frisk was sitting in bed, holding a tightly-swaddled newborn baby girl. The baby seemed to take more after Asriel, though she had a few dark brown spots in her white fur and a set of blue eyes instead of red ones. They named her Charlotte, after Asriel's sister, Chara.

It was the beginning of a new chapter.

* * *

 **And that's it! The most lemony story I've ever written!**

 **A tiny bit of news: I have a DeviantArt page! Just look up KristenGaster to find me! If you want to check out my Wattpad account, same name!**

 **If you have a friend who is a fan of my ImmortalTale story, please tell them that chapter ten** _ **is**_ **in progress and I haven't abandoned it. I would greatly appreciate it.**

 **So long and thanks for all the fish!**


End file.
